[Help] Join query from 3 tables

Question

Hi, I'm new to database. I have a question about joining 3 tables, pardon me for my bad english.
My tables look like this
table 1: Person (id,firstname, lastname)
table 2: AssignPersonAddress (id,personid,addressid,type)
table 3: Address (id,telefon, street, etc)
I need AssignPersonAddress table, because in my data structure a person can have more than 1 address and the address type should be saved (for eg: private, work)
I want to make a select query to report all of person with his private telefon and work telefon, like this.
PERSON | PRIVATE | WORK
At the moment my query looks like this
select p.name , a1.tel AS Private, a2.tel AS Work
from person p,
addresse a1 ,
AssignPersonAddress apd1,
AssignPersonAddress  apd2,
addresse a2
where p.id  = apd1.person (+)
and apd1.adresse  = a1.id
and apd1.art = 'Private'
and p.objectid = apd2.person (+)
and apd2.adresse  = a2.id
and apd2.art = 'Work'the problem is I only get the person who has private and work address. But what I want is all person no matter if the person has only 1 address or 2 address.
As you can see I put the outer left join at the where condition, but I'm still getting the wrong result.
thx in advance
Danny
Edited by: raitodn on Oct 1, 2009 3:51 AM
Edited by: raitodn on Oct 1, 2009 4:12 AM

Answer 1

Hi,
You're essentially doing an inner join, because some of the comparisons are missing the + markerr.
Do this instead:
select  p.name , a1.tel AS Private, a2.tel AS Work
from      person                p
,      addresse           a1
,      AssignPersonAddress      apd1
,      AssignPersonAddress      apd2
,      addresse           a2
where      p.id           = apd1.person (+)
and      apd1.adresse      = a1.id (+)
and      apd1.art (+)     = 'Private'
and      p.objectid      = apd2.person (+)
and      apd2.adresse      = a2.id (+)
and      apd2.art (+)     = 'Work'
;What does this mean?
where      p.id           = apd1.person (+)It means "include rows from p even if they don't have any matching rows in apd1". Whenever that happens, all the colummns from apd1 will be NULL.
So far, so good.
Now, what happens if you follow that with
and      apd1.adresse      = a1.id The condition above means "include this row from apd1 only if there is matching row in a1". If apd1 is NULL, this condition will never be TRUE (even if a1.id is NULL).
When you do a cascading outer join like this, all columns in the distal table (the table farther away from the table that must be present) need to be marked with the + sign. That includes conditions involving a constant, like
and      apd1.art (+)     = 'Private' By the way, when posting code or results on this site, always type these 6 characters:
(small letters only, inside curly brackets) to preserve spacing and to keep some strings, such as the outer-join marker, form being interpreted as emoticons.
Edited by: Frank Kulash on Oct 1, 2009 6:37 AM
Added explanation